A steam turbine converts the kinetic or thermal energy of pressurized steam into useful mechanical work. Generally described, the steam is created in a steam generator or a boiler, passes through control valves and stop valves into the sections, and drives a rotor assembly. The rotor assembly then in turn may drive a generator to produce electrical energy and the like. The control valves and the stop valves control the operation of the steam turbine by controlling the flow of the steam into the sections. A control valve typically controls or regulates the volumetric flow and/or the pressure of the steam entering into the sections during normal operation levels. A stop valve is typically a safety valve. The stop valve is typically held open during normal operation and closed when immediate shutdown is necessary. In some applications, the control valve and the stop valve may be integrated into a single unit.
Due to market demands, steam turbines may be required to operate with increased cycling and longer inspection intervals. In order to obtain significant information about the condition of the steam turbine components, such as the control valves and the stop valves, condition monitoring systems may be used. Such monitoring systems, however, may be limited in scope in that certain types of component wear or damage may only be apparent via visual inspection during a system shutdown. Such outage costs and time may be significant.